In many mechanisms and devices there is a need to convert motion of one type to another. When converting from linear motion to rotary motion, cranks are often used. This is the case in most internal combustion engines. It is well known that the crank and slider mechanism suffers in mechanical advantage of transferring linear forces of the pistons to a crank by a connecting rod. When pressures are highest in the combustion chamber, the mechanical advantage of transferring that force from the piston to torque on the crank is poor. By the time the piston has good mechanical advantage because of the angle of the crank, the pressures are being reduced because of expansion and cooling.
The current invention transfers a bidirectional oscillating rotary motion from a pendulum type engine to rotary output. It has good mechanical advantage for practically all of the power stroke. Rather than momentarily having good mechanical advantage as with the crank and slider, it momentarily has a needed poor mechanical advantage as the oscillating pendulum engine changes direction of rotation. Mechanical advantage is good even when pressures are highest. This can be a key to efficiently and effectively transferring forces from an engine to torque of a rotational output.
It is known that with a hypocycloid gear set where there is a stationary ring gear with a planet gear of exactly half the diameter meshing within it, a selected point at the pitch circle of the planet gear travels in a linear path through the diameter of the ring gear. The same thing can be done without gears by using three linear bearings going to three points on what would be the pitch circle of the planet gear. A similar effect was invented by Cardano in the 16th century. His gear set used a stationary sun gear rather than the stationary ring gear and two planet gears meshing with each other. The same effect can be done by using sprockets and chains, or with cogged pulleys and belts. The current invention makes use of the principles of those devices which convert between rotary motion and linear motion without using a crank.
The preferred embodiment of the apparatus of the current invention has exactly the same behavior in both directions of oscillation. Exactly half a turn of the rotary shaft is used for each direction of the oscillation in some embodiments, or in other embodiments a full rotation of the rotary shaft yields one direction of oscillation. Also, acceleration and deceleration of the oscillating member is the same for both directions in some embodiments, or behavior can be altered in other embodiments. And the force is more efficiently transferred in the apparatus of the current invention than in other solutions. This apparatus can find uses anywhere where its motion conversion can be beneficial, but was designed with the goal of transferring forces of oscillating rotary motion from a pendulum type engine to torque in continuous rotary motion.
The apparatus of the current invention can also find uses in other types of motion conversion besides oscillating to rotary or rotary to oscillating. By holding what would be the rotary member stationary and instead rotating what would have been the stationary member, what would be the oscillating member has a rotary motion with a momentary dwell. Other behaviors can also be caused with a combination of inputs.
The four bar crank and rocker mechanism has the rotary motion on one axis and the oscillating motion on another axis. The current invention can have both on the same axis. Where it is desirable for both motions to be on the same axis, the apparatus of this invention may have extra value.